At the end of the previous passage, 2:10, Paul had flagged up the importance of living out the Gospel. The “poor” refers particularly to the needy churches in Judea, who needed the support of their gentile brothers and sisters. They were not two unrelated families, but one family, and it was important that they continue to recognise that and live that out. Living out the truth of the Gospel is the concern here as he remembers a very public disagreement with Peter over what “living in line with the truth of the Gospel” (2:14) should look like.
It is somewhat surprising that Paul should remind the Galatians of this disagreement, given his concern to show that he was on the same page as the other apostles; this might seem to undermine what he was saying. Of course it does show his authority, and shows how deeply concerned Paul was that the Gospel should not only be believed and preached, but lived out. The Gospel can be undermined by what we do as well as by what we say.
Since his vision in Acts 10 and visit to Cornelius, Peter had been clear that the food laws were no longer binding and that Gentiles Christians shared equally in the blessings of the Gospel, and so when he first arrived in Antioch he had been very happy to share meals with his Gentile brothers and sisters. The arrival of “some men from James” changed that. If these were the same people as the “circumcision group”, then it seems they claimed a loyalty to James even if not having his full endorsement, and were insisting that Gentile Christians needed to be circumcised to share fully in the covenant blessings. Peter’s fear of them is surprising perhaps, since he was an apostle (but then he had been frightened of the high priest’s servant girl). Perhaps he wanted to avoid a conflict and thought it best to appease them. It is possible (and to my mind slightly more probable) that the circumcision group refers to (nationalist) Jews in Judea. The men from James may simply have been messengers come to tell Peter of the unintended impact his actions were have on the church in Jerusalem. If it had become known that this pillar of the church was disregarding the Law, it might well have led to increased persecution of the church in Judea. This puts a slightly better spin on Peter’s actions, and presumes he decided to revert to kosher ways for the sake of his brothers and sisters back home – a pragmatic decision, which other Jews in the church followed him in.
Paul though told Peter that his pragmatism was undermining his Gospel principles. By withdrawing from his Gentile brothers and sisters, the message he was effectively giving them was “If you want to be in true fellowship, you must be circumcised” – not a message Peter believed, but one his actions gave. He was “not acting in line with the Gospel”. We might be clear on what we believe, but we should ask ourselves: do our actions, how we relate to others at church, suggest something different? We might be polite to all, but only really enjoy close fellowship with those who trust Jesus AND … share a similar background or whatever. Notice too how his hypocrisy spread and led others astray (v.13)
Paul is clear that this is about the Gospel, how we are justified. Our standing with God is not at all determined by our obedience to the Law but “by faith in Jesus Christ” – Peter and Paul both knew the Law justified no one. Jewish opponents, it seems (v.17), claimed that Christ promoted sin, because Jewish Christians were associating freely with “sinners” (ceremonially unclean Gentiles), but Paul says (v.18) that to go back to the Law (ie to “rebuild what I destroyed”) would only show that he was “a law-breaker”, since the Law will not justify us but only expose our sin and the Law was to lead us to Christ (not away from him).
The final paragraph is worth dwelling on. It speaks of our union with Christ – union in his death and in his life. In dying with Christ, we died to the Law – its demands were satisfied. You might like to recall the four things the Bible says were nailed to the cross – Jesus (obviously), the charge they killed him for (“King of the Jews”), the charge that stood against us because of our sins (so Colossians 2:14), and … us – we were crucified with Christ (v.20). And so the Law now has no hold over us. We share too in Christ’s resurrection life – new life with a new focus and wonderful confidence. To “live by faith in the Son of God” is to live trusting not in what we do but what Christ has done and to live with the understanding of who we are in Christ – perfectly loved and made holy.